Method and apparatus for alarming decrease in tire air-pressure, and program for judging decompression of tire

Abstract

A method for alarming decrease in tire air-pressure. The method includes the steps of: detecting rotational information of respective tires; respectively calculating and storing a wheel speed, a vehicle acceleration, a slip ratio between front and rear wheels, a running distance and a turning radius; accumulating the running distance, the moving-averaged vehicle acceleration and the slip ratio between front and rear wheels; obtaining a linear regression coefficient and a correlation coefficient of the vehicle acceleration and the slip ratio; judging whether at least a driving wheel tire has decompressed upon comparing a judged value of the linear regression coefficient and a reference value for internal pressure of the linear regression coefficient; and issuing an alarm of decrease in tire air-pressure. It is possible to improve performance and safety of the vehicle since it is possible to detect decompression of tires including at least one driving wheel tire, for instance, of not less than two wheel tires including the right and left driving wheels.

What is claimed is:  
     
       1. A method for alarming decrease in tire air-pressure, which alarms decrease in internal pressure of a tire on the basis of rotational information obtained from tires attached to a vehicle, the method comprising the steps of: detecting rotational information of respective tires; respectively calculating and storing a wheel speed, a vehicle acceleration, a slip ratio between front and rear wheels, a running distance and a turning radius on the basis of the rotational information of the respective tires; performing moving averaging of the vehicle acceleration and the slip ratio between front and rear wheels; accumulating the running distance, the moving-averaged vehicle acceleration and the slip ratio between front and rear wheels when the turning radius is not less than a specified value; obtaining a linear regression coefficient and a correlation coefficient of the vehicle acceleration and the slip ratio between front and rear wheels when the accumulated running distance has reached a specified distance; judging whether at least a driving wheel tire has decompressed upon comparing a judged value of the linear regression coefficient and a reference value for internal pressure of the linear regression coefficient which has been preliminarily calculated in the above step when the tires are reference internal pressure, the linear regression coefficient when the correlation coefficient is not less than a specified value being set as the judged value; and issuing an alarm of decrease in tire air-pressure on the basis of the result of judgment of decompression. 
     
     
       2. The method of  claim 1 , wherein the method further includes the steps of calculating amount of fluctuation in a difference between respective slip ratio of the front and rear wheels on the left-hand side and that of the front and rear wheels on the right-hand side, and correcting the linear regression coefficient in accordance with an average fluctuation amount of the amount of fluctuation per each specified distance of the running distance. 
     
     
       3. The method of any one of claims  1  or  2 , wherein the method further includes the step of issuing an alarm to inspect an air-pressure of a tire when the initialization switch has not been operated or when a total running distance until the initialization switch is repeatedly operated after the initialization switch has been operated once. 
     
     
       4. An apparatus for alarming decrease in tire-air-pressure, which alarms decrease in internal pressure of a tire on the basis of rotational information obtained from tires attached to a vehicle, the apparatus comprising: rotational information detecting means which detects rotational information of respective tires; a first calculating means which respectively calculates and stores a wheel speed, a vehicle acceleration, a slip ratio between front and rear wheels, a running distance and a turning radius on the basis of the rotational information of the respective tires; a second calculating means which performs moving averaging of the vehicle acceleration and the slip ratio between front and rear wheels; an accumulating means which accumulates the running distance, the moving-averaged vehicle acceleration and the slip ratio between front and rear wheels when the turning radius is not less than a specified value; a third calculating means which obtains a linear regression coefficient and a correlation coefficient of the vehicle acceleration and the slip ratio between front and rear wheels when the accumulated running distance has reached a specified distance; a decompression judging means which judges whether at least a driving wheel tire has decompressed upon comparing a judged value of the linear regression coefficient and a reference value for internal pressure of the linear regression coefficient which has been preliminarily calculated when the tires are reference internal pressure, the linear regression coefficient when the correlation coefficient is not less than a specified value being set as the judged value; and an alarming means which issues an alarm of decrease in tire air-pressure on the basis of the result of judgment of decompression. 
     
     
       5. The apparatus of  claim 4 , wherein the apparatus further includes a fourth calculating means which calculates an amount of fluctuation in a difference between respective slip ratio of the front and rear wheels on the left-hand side and that of the front and rear wheels on the right-hand side, and a regression coefficient correction means which corrects the linear regression coefficient in accordance with an average fluctuation amount of the amount of fluctuation per each specified distance of the running distance. 
     
     
       6. The apparatus of any one of claims  4  or  5 , wherein the apparatus further includes a second alarming means which issues an alarm to inspect an air-pressure of a tire when the initialization switch has not been operated or when a total running distance until the initialization switch is repeatedly operated after the initialization switch has been operated once. 
     
     
       7. A computer program on a computer readable medium for judging decompression of a tire, wherein a computer is made to function, for judging decrease in tire air-pressure, as a first calculating means which respectively calculates and stores a wheel speed, a vehicle acceleration, a slip ratio between front and rear wheels, a running distance and a turning radius on the basis of the rotational information of the respective tires; a second calculating means which performs moving averaging of the vehicle acceleration and the slip ratio between front and rear wheels; an accumulating means which accumulates the running distance, the moving-averaged vehicle acceleration and the slip ratio between front and rear wheels when the turning radius is not less than a specified value; a third calculating means which obtains a linear regression coefficient and a correlation coefficient of the vehicle acceleration and the slip ratio between front and rear wheels when the accumulated running distance has reached a specified distance; and a decompression judging means which judges whether at least a driving wheel tire has decompressed upon comparing a judged value of the linear regression coefficient and a reference value for internal pressure of the linear regression coefficient which has been preliminarily calculated when the tires are of reference internal pressure, the linear regression coefficient when the correlation coefficient is not less than a specified value being set as the judged value. 
     
     
       8. The computer program on a computer readable medium of  claim 7 , wherein the computer is further made to function as the fourth calculating means which calculates an amount of fluctuation in a difference between respective slip ratio of the front and rear wheels on the left-hand side and that of the front and rear wheels on the right-hand side, and the regression coefficient correction means which corrects the linear regression coefficient in accordance with an average fluctuation amount of the amount of fluctuation per each specified distance of the running distance.